The present invention relates in general to surgical stapler instruments which are capable of applying lines of staples to tissue while cutting the tissue between those staple lines and, more particularly, to improvements relating to stapler instruments and improvements in processes for forming various components of such stapler instruments.
Surgical staplers have been used in the prior art to simultaneously make a longitudinal incision in tissue and apply lines of staples on opposing sides of the incision. Such instruments commonly include a pair of cooperating jaw members which, if the instrument is intended for endoscopic or laparoscopic applications, are capable of passing through a cannula passageway. One of the jaw members receives a staple cartridge having at least two laterally spaced rows of staples. The other jaw member defines an anvil having staple-forming pockets aligned with the rows of staples in the cartridge. The instrument includes a plurality of reciprocating wedges which, when driven distally, pass through openings in the staple cartridge and engage drivers supporting the staples to effect the firing of the staples toward the anvil.
The wedges are commonly formed from metal and assembled in a pusher block to form a single component. Since a number of individual parts must be assembled to form this component, it is costly to manufacture. Also, such components, because they are comprised of a number of individual parts, oftentimes have less than optimum stability. Further, it has been found that use of metal wedges results in a high coefficient of friction between the wedges and the drivers during staple firing.
The prior art wedges generally include a straight, single-angle cam surface. The cam surface is designed to provide sufficient force for bending over ends of the staples. While the cam design performs the desired operation, it also results in an undesirable increase in the overall length of the instrument.
Prior art mechanisms for driving wedges distally into a staple cartridge commonly include a firing mechanism and a motion transfer mechanism. The firing mechanism is engaged by a surgeon to effect staple firing. Most currently available motion transfer mechanisms, which are interposed between the firing mechanism and the pusher block, are not easily modifiable for use in stapler instruments having different staple line lengths and/or staple firing force requirements so as to permit, for a given instrument, the length of the stroke of the firing mechanism and the force required to move it to be set at ergonomically preferred values.
Accordingly, there is a need for an improved stapler instrument. Preferably, such an instrument would have wedges integrally formed as a single unit. Also, the improved stapler instrument would have wedges which are formed from an improved material such that the coefficient of friction between the wedges and the drivers during staple firing is reduced over that found in the prior art. The improved stapler would also have wedges provided with a more efficient cam surface profile. There is further a need for an improved motion transfer mechanism which is easily adaptable for use in various stapler instruments having different stable line lengths and/or staple firing force requirements so as to permit, for a given instrument, the length of the stroke of the firing mechanism and the force required to move it to be set at ergonomically preferred values.